Touching in at platform 1/2 before 7/8 works, thanks:

(details put into what seems a more logical order to me)

07:12 Touch in, New Barnet [National Rail] £8.30 £15.85
07:31 Touch out, Finsbury Park [London Underground / National Rail] +£4.40 £20.25
07:12 – 07:31 New Barnet [National Rail] to Finsbury Park [London Underground / National Rail] £3.90 £20.25
08:15 Touch in, Finsbury Park [London Underground / National Rail] £8.30 £11.95
08:15 Touched pink card reader, Finsbury Park [National Rail] £0.00 £11.95
08:32 Touch out, New Barnet [National Rail] +£4.40 £16.35
08:15 – 08:32 Finsbury Park [London Underground / National Rail] to New Barnet [National Rail] £3.90 £16.35

Later in the week I was continuing into Moorgate. I left at Finsbury Park, got on with my business and then entered Drayton Park to continue to Moorgate. At Drayton Park the validators (no gates there) registered me as exiting, presumably because I was within the 100 minute journey time, so at Moorgate I had an incomplete journey 🙁

07:11 Touch in, New Barnet [National Rail] £8.30 £28.05
07:31 Touch out, Finsbury Park [London Underground / National Rail] +£4.40 £32.45
08:26 Touch out, Drayton Park [National Rail] £0.00 £32.45
07:11 – 08:26 New Barnet [National Rail] to Drayton Park [National Rail] £3.90 £32.45
???? – 08:46 [No touch-in] to Moorgate £8.40 £24.05

I’m not sure the benefit of continuing from Drayton Park and being charged incorrectly is worth it for me compared to returning to Finsbury Park and touching back in at platforms 1/2, which will presumably work, so I’ll probably do that in the future. Seems a shame to plan journeys around the quirks of a ticketing system like Oyster.

The failed journey is:

???? – 09:30 [No touch-in] to New Barnet [National Rail] £3.75 £12.75

I hadn’t thought to look in the previous journey. That is:

07:41 – 08:01 New Barnet [National Rail] to Finsbury Park [London Underground / National Rail] £3.90 £16.50
09:11 Touched pink card reader, Finsbury Park [National Rail] £0.00 £16.50
08:01 Touch out, Finsbury Park [London Underground / National Rail] +£4.40 £16.50
07:41 Touch in, New Barnet [National Rail] £8.30 £12.10

So a 70 minute gap. I understand the need for the EOSI but more than an hour at Finsbury Park, especially when if you are waiting for a train you are likely to do that on the platform there, seems too long.

The times I was charged a maximum fare are 59 and 65 minute gaps.

What I’m after is a way for this to not happen. I’m expecting to make this journey a couple of times a week for the next few months and I can’t get a refund online when they get it wrong.

As for FCC/GTR, I’m aware of that. Bit disappointed that the TfL Oyster helpline person had such old information though 🙁